Many modern integrated circuits, especially those of the microprocessor type, now integrate upwards of hundreds of thousands of transistors into a single semiconductor chip to provide a high degree of functionality at very high speeds. Even when utilizing low-power technologies such as complementary metal-oxide-semiconductor (CMOS) technology, these ultra-large-scale integrated (ULSI) circuits dissipate significant electrical power, for example more than one watt.
As is well known in the art, the electrical power dissipated in an integrated circuit is often manifest as thermal energy in the semiconductor chip. This thermal energy will tend to elevate the temperature of the semiconductor chip. As is well known in the art, both the switching speed and the reliability of an integrated circuit decrease with increasing temperature. As a result, integrated circuit package design is highly concerned with the conduction of thermal energy away from the semiconductor chip, such conduction taking place through the package, in an attempt to minimize performance and reliability degradation due to high operating chip temperatures.
Referring now to FIG. 1, a conventional integrated circuit package for providing high thermal conductivity is illustrated. In this example, the semiconductor chip is housed within pin-grid-array package 2. As is conventional in the art, pin-grid-array package 2 is a ceramic header, within which the semiconductor chip is mounted and its conductive terminal pads bonded, by wire bonds or the like, to pins extending from the bottom of pin-grid-array package 2; a ceramic or metal lid is then bonded to the header by way of glass reflow, brazing, or by way of other conventional techniques. In the example shown in FIG. 1, heat sink 4, of the "pin-fin" type, is mounted to the top surface of pin-grid-array package 2. Heat sink 4 is conventionally formed of extruded aluminum or another thermally conductive material, and includes a flat lower portion 4f that is attached to pin-grid-array package 2 by way of a thermally conductive epoxy, or by other conventional means.
The upper portion of heat sink 4, as shown in FIG. 1, includes a large number of finger-like extensions, or pins, 4e extending away from pin-grid-array package 2. Extensions 4e are responsible for nearly all of the surface area of heat sink 4. As such, extensions 4e will provide a highly thermally conductive path from pin-grid-array package 2 to the atmosphere thereabove, without greatly increasing the overall height of the package combination. Especially if a flow of cool air passes over and through extensions 4e, conventional heat sink 4 can be quite useful in removing thermal energy from the semiconductor chip packaged in pin-grid-array package 2.
However, considering that heat sink 4 is generally attached to pin-grid-array package 2 by the manufacturer of the integrated circuit, the arrangement of FIG. 1 suffers from certain limitations. Firstly, many computer and system manufacturers use vacuum pickup tools to transport and install packaged integrated circuits into circuit boards; this is especially the case for system manufacturers that use automated pick-and-place robotic machines in circuit board assembly. However, vacuum pickups cannot readily be used with the arrangement of FIG. 1, as there is not adequate planar surface area on its top to allow a vacuum pickup to reliably attach to heat sink 4 (and thus to lift and transport pin-grid-array package 2). This may require manual installation of the package of FIG. 1, at greater cost and often reduced accuracy.
Secondly, there is also not enough coplanar surface area on the upper surface of the integrated circuit package of FIG. 1 to allow the manufacturer or purchaser of the integrated circuit to mark the packaged circuit with a code, part number, or manufacturer identification. Particularly if multiple integrated circuits similarly packaged are to be mounted to the same circuit board, the arrangement of FIG. 1 can result in manufacturing defects in the end system with the wrong integrated circuit mounted at the wrong circuit board location.
It is therefore an object of the present invention to provide an integrated circuit package utilizing pin-fin thermal conduction and that may be mounted by vacuum pickup equipment.
It is a further object of the present invention to provide such an integrated circuit package that allows for topside symbolization and marking after manufacture.
Other objects and advantages of the present invention will become apparent to those of ordinary skill in the art having reference to the following specification together with its drawings.